Let's just get right into this: President Trump in an interview doesn't seem to know why the Civil War happened and also seems to think that "people" don't ask questions about it. Here's the audio clip:

Here's the answer, President Trump: Slavery. The Civil War happened because of slavery in the United States. And Andrew Jackson, the seventh president, owned slaves and a plantation. And he died in 1845 — the Civil War began in 1861.